1. Field of the Invention
The present invention relates to a switch contact for a vacuum switching tube.
2. Description of the Prior Art
A switch contact for a vacuum switching tube is disclosed by U.S. Pat. No. 4,196,327 comprising a means for generating an axial magnetic field which comprises a stud and a contact member having at least one contact surface and contains two or more conductor loops at the side facing away from the contact surface, whereby the conductor loops generate a magnetic field proceeding in axial direction over the contact surface, whereby the conductor loops proceed from the stud and return to a region of the switch member close to the axis and comprise terminals separated from one another by a slot, whereby the terminals of the conductor loops are supported in the direction toward and in the proximity of the axis of the stud by a supporting member having poor electrical conductivity or no electrical conductivity and whereby the conductor loops are connected to one another of one piece at least in their part remote from the axis. Essentially two embodiments can be derived from this patent, one embodiment allowing the current to pass into a contact member in the region of the outer circumference, and a second embodiment which returns the current into the proximity of the rotational axis of the contact and allows it to pass there into corresponding contact surfaces of the contact member.
The first of the embodiments which allows the current to pass into the contact member in the region of the outer circumference of the conductor loop yields a field strength of the axial magnetic field which is dependent on the distance of the arc from the edge of the conductor loop. This non-uniformity of the magnetic field is undesirable. The second embodiment avoids this non-uniformity of the magnetic field but is relatively involved in terms of manufacture, since a horizontal slot must be manufactured within a ring, a special tool being required for this purpose. This embodiment, on the other hand, does not allow a dimensioning to maximum load of the material since the webs leading to the center of the ring and, thus, to the contact surfaces can only comprise a small part of the height of the conductor loops in the region of the circumference. An extremely wide construction of the webs would inadmissably diminish the area permeated by the axial field. Thus, a high weight of the conductor loop in comparison to the power must be accepted given this embodiment.